Axinite

Chemistry: Complex calcium aluminum borosilicate
Crystal system: Triclinic; bladed, wedge-shaped crystals; lamellar masses
Color: Transparent to translucent; brown, more rarely yellow, violet, blue.
Hardness: 6.5 - 7
Cleavage: Perfect: in one direction; Fracture: brittle, conchoidal to uneven.
Specific gravity: 3.28 (3.27 – 3.29)
Refractive index: 1.675 – 1.685; Biaxial negative; 0.010 – 0.012
Luster: Greasy to vitreous
Dichroism: Strong; olive to strong green/violet blue; brown/yellow.
Occurrence: In areas of contact metamorphism; France, Mexico, USA, Sri Lanka, Pakistan.

Notes
Axinite is named after axe-like shape of crystals. The specimens may look like smoky quartz; piezo electric; no luminescence in gem quality specimens but may show in yellow as reddish glow; some show phosphorescence; spectrum: yellow—3 bands, 1 narrow in blue/green, 2 broaded in blue 512, 492, 466nm; faceted for collectors.